1. Field of the Invention
The present invention relates generally to cameras and particularly to an automatic focusing camera having a function of detecting camera-shake and operating in a plurality of operation modes.
2. Description of the Related Art
Recently, there have been proposed automatic focusing cameras having various operation modes. Such cameras are controlled by an operation mode most suitable for conditions of an object.
Japanese Patent Laying-Open No. 61-286809 discloses a focusing apparatus which detects a shake amount of an object image and a focal length of a taking lens, compares the shake amount with an image shake permissible value based on the focal length, and controls the drive of a focusing drive lens based on the result of the comparison. This focusing apparatus makes it easy to set an in-focus state by excluding unreliable focus information due to camera-shake and to maintain the in-focus state after the focusing.
In such a conventional camera having the above-mentioned focusing apparatus, even if camera-shake is detected, operation modes are not changed based on the result of the detection. Consequently, the camera is liable to be controlled based on a rather incorrect operation mode dependent on camera-shake.
If an operation mode is to be suitably set by using information on camera-shake, degrees of camera-shake are different dependent on photographers and consequently an appropriate operation mode cannot be set.
An automatic focusing camera using a measured focus detection value indicating a distance to an object as information for switching of operation modes has been proposed.
Such an automatic focusing apparatus intends to easily set an in-focus state by excluding unreliable focus information affected by camera-shake and to maintain the in-focus state.
In such a conventional camera, an operation mode is determined only by the measured focus detection value and if a change in object brightness occurs together with a change in the distance to the object due to panning, it is not possible to determine an appropriate operation mode by suitably detecting such conditions.
Therefore, there have been also proposed cameras having a function of automatically switching operation modes based on various information.
In such a conventional camera having the function of automatic switching of modes, the switching of modes is controlled by crisp determination (binary determination) of various photographing information (such as defocus information, a photographing magnification, and brightness of an object) obtained in a time-sequential manner. Such crisp determination has, however, a limitation in an amount of information to be handled for determination of conditions of the object and it is difficult to reflect sufficient information on switching of operation modes. In addition, if various types of information are combined in order to enhance the precision of switching control, the control becomes complicated and a small change in the information would affect switching of operation modes, making the control unstable.
In addition, in such a conventional camera having the function of automatic switching of operation modes, if a special brightness change as in the case of framing (setting a composition after automatic focusing) occurs, an appropriate operation mode cannot be selected and erroneous operation sometimes occurs.